…which economists refer to as “high Tobin’s Q.”… The authors test eight alternative theories…. About a third of the decline in measured investment can be explained by a shift towards intangible assets. Among the remaining theories… only decreased competition (if firms don’t need to invest in new equipment or strategies to stay competitive, why would they?), tightened governance and, potentially, increased short-termist pressures help explain the phenomenon…. Changes in competition and governance seem partly explained by changes in policy (regulations, anti-trust) and in asset management (activism, indexing, and pressure for shares buyback programs)…